The massive neolithic architecture of western Europe begins, in the 5th millennium BC, with 'passage' graves. The name reflects the design. A stone passage leads into the centre of a great mound of turf, where a tomb chamber - first of wood but later of stone - contains the dead of the surrounding community.

A famous early example of a stone passage grave, from about 4000 BC on the Île Longue off the coast of Brittany, has a magnificent dome formed by corbelling (each ring of stone juts slightly inwards from the one below). It is the same principle as the beehive tombs of Mycenae, but they are more than 2000 years later.

Over the centuries increasingly large slabs of stone, or megaliths (from Greek megas huge and lithos stone), are used for the passage graves. And an astronomical theme is added. The graves begin to be aligned in relation to the annual cycle of the sun.

An outstanding example is the passage grave at Newgrange in Ireland, dating from about 2500 BC. The huge slabs of stone which form the walls of the chamber are carved in intricate spiral patterns. At sunrise on the winter solstice (the shortest day of the year, when the sun itself seems in danger of dying), the rays penetrate the length of the passage to illuminate the innermost recess.

In a later stage of this deeply mysterious Neolithic tradition the megaliths, previously hidden beneath the mounds of the tombs, emerge in their own right as great standing stones, often arranged in circles. The ritual purpose of such circles is not known. They too, in many cases, have a solar alignment, usually now relating to sunrise at the summer solstice.

The most striking of these circles is Stonehenge, in England. The site is in ritual use over a very long period, from about 3000 to 1100 BC. The largest stones, with their enormous lintels, are erected in about 2000 BC.